All new electrified vehicles must emit a noise at low speeds to warn pedestrians of their presence under new EU law.
The ruling applies at all four-wheeled fully electric and hybrid vehicles that go on sale from July 1. Under the regulation, electric vehicles must have an Acoustic Vehicle Alert System (AVAS) that activates at speeds below 20kph (12mph) and be at a minimum noise level of 56dB.
According to experts IAC Acoustics, 60dB would be the equivalent of conversation in an office or standing 100ft from an air conditioning unit, and about half as loud as a vacuum cleaner.
Some car manufacturers already have AVAS fitted to their vehicles, such as Jaguar with its I-Pace, which emits a science-fiction UFO-like warble below 12mph to warn pedestrians of its approach.